The use of complex compounds, zeolites, activated carbon, metal hydrides and metal oxide-hydroxide reaction compositions as heat pump working materials is known in the art. Complex compounds are materials formed by adsorption of gas molecules on a solid adsorbent. Suitable complex compounds comprise metal salts on which gaseous ligands such as water, ammonia, methanol, methane, ethane and the like are alternately adsorbed and desorbed. A number of such materials are described in co-pending applications Ser. Nos. 115,820, filed Nov. 2, 1987 and Ser. No. 162,016, filed Feb. 29, 1988 now U.S. Pat. Nos. 4,822,391 and 4,848,994, respectively. These complex compounds are highly advantageous in heat pump technology, thermal storage or in other heat-transfer systems, since they are relatively inexpensive, yield higher refrigerant density as compared to liquid-vapor media, and are useful in relatively simple and inexpensive heat pump apparatus. The specific complex compounds and their uses described in the aforesaid co-pending applications are incorporated herein by reference. Other solid-gas reaction systems, such as metal hydrides, inclusion compounds (zeolites and activated carbons), and metal oxide-hydroxide and metal oxide-carbonate reactions have application as heat pumps, refrigeration and power cycle working media, desiccants, scrubbers, adsorbents for solvent recovery, or thermal energy storage. The subject invention is applicable to all such systems.
Solid-gas adsorption and desorption reactions are generally accompanied by significant volume and density changes of the solid material. Such solid-gas reactions are typically conducted in fluidized beds, on flat plate heat exchange surfaces on which the solid reactant is located, or with heat transfer and gas flow tubes embedded in a mass of solid reactant. These systems allow free expansion of the solid reactant. However, if the solid is allowed to expand without restriction, a large void fraction results thereby substantially reducing composition density with concomitant reduction of thermal conductivity and reaction rates because of limited heat transfer in the solid mass and at the interface. It is an object of the present invention to reduce or obviate such problems.